The present invention relates to a high output wafer-shaped semiconductor device which is tightly sealed by a plastic coating. More particularly the present invention relates to such a semiconductor device including a wafer-shaped semiconductor body provided with major electrodes at its two opposed major surfaces, two cylindrical metal bodies, serving as current connecting means and heat dissipating means, contacting the semiconductor body at its respective major electrodes, and a ring of insulating material which encloses and centers the metal bodies and the semiconductor body.
Wafer-shaped semiconductor devices of the above type are commercially available. The insulating ring in these components is generally made of plastic or ceramic. Insulating parts of plastic, e.g. a type of silicone, can be manufactured less expensively than insulating parts of ceramic so that plastic parts are preferred. It has been found, however, particularly with high output semiconductor components which are to be embedded in plastic, that it is extremely difficult to shape and structure the plastic parts of the semiconductor device in such a way that the plastic embedding mass provides a seal which is resistant against the influences of alternating thermal stresses. Alternating stresses produce internal mechanical stresses in a device of the above-described type due to the different coefficients of thermal expansion of the metal bodies which contact the semiconductor body on the one hand, and the plastics employed for encasing the device and for the insulating ring, which stresses may lead to the formation of cracks in the plastic parts.